1. Field of the Invention
The present invention relates generally to power management, and more particularly to a method of reducing power consumption in a portable electronic device.
2. Description of Related Art
Continued advancements in telecommunication technologies have made mobile phones, smartphones and other portable electronic devices very popular. Because talk time and standby time are important performance attributes of such devices, techniques for extending battery life or otherwise reducing power consumption are becoming increasingly important.
To extend battery life, a smartphone may enter a low power mode (or sleep mode) when it is idle, that is, when the smartphone is on but there is no interaction with any user or any user terminal. While in sleep mode, a phone may turn off much of its circuitry until the smartphone is awakened, e.g., by a user input or an incoming call. However, the external memory of existing smartphones, e.g., DDR (Double Data Rate memory) or SDRAM (Synchronous Dynamic Random Access Memory), cannot be fully powered down and has to be put into a self refresh mode or other low power mode which can retain the content of the external memory. One reason behind this is to avoid missing incoming calls, since the smartphone needs to acknowledge an incoming call in a few milliseconds, but it may take much longer to restore the external memory and the operation of the phone if the external memory is fully powered down.
A laptop computer may use the hibernate feature to save battery power, where the content of its RAM may be written to non-volatile storage, such as a hard disk drive, before powering down the system. When being turned on again, the system can be restored to the state it was in when the hibernation was invoked, so that programs can continue to be executed as if the hibernation never happened. Although resuming from hibernation is faster than a hard reboot, it may take several seconds, much longer than the time in which a smartphone is required to acknowledge an incoming call.
Since keeping external memory of a smartphone in self refresh mode consumes considerable power, it may be desirable to provide a method and apparatus which can reduce power consumption of a smartphone while in sleep mode.